Littelfuse MPU Series Modules - MPU-CIM-00-00

Technical Dossier

Product Details And Specifications

Littelfuse MPU Series Technical Notes

The Evolution of MPU Series Architecture

The Littelfuse MPU Series originated from the POWR-GARD product line, which Littelfuse acquired through its purchase of ESCO Technologies' relay division. Early-generation MPU units (MPU-32 platform) used discrete analog input cards with RS-485 Modbus RTU as the primary communications interface. These units were designed for standalone MCC bay deployment with limited SCADA integration capability.

The second-generation MPU architecture introduced a modular backplane system, separating the CPU module from analog input, digital input, and communications adapter modules. This allowed field-upgradeable firmware and hot-swap-compatible I/O expansion without full relay replacement. The MPU-32 evolved into the MPU-32E with expanded event logging (up to 1,024 events) and enhanced harmonic analysis capability up to the 31st harmonic.

Current-generation MPU modules support dual-port Ethernet with EtherNet/IP and Modbus TCP protocols, enabling direct integration with Rockwell Automation ControlLogix and Siemens S7 PLC environments. Compatibility issues arise when mixing first-generation analog input modules (MPU-AIM-xx-xx) with third-generation CPU modules due to backplane register map changes introduced in firmware v3.x. Plants operating mixed-generation MPU fleets must maintain firmware version discipline across all chassis slots.

MPU Series Full Catalog & Functionalities (SKU List)

Current Input Modules (CIM)

• MPU-CIM-00-00: Standard 3-phase current input module, 1A/5A CT secondary, no ground fault
• MPU-CIM-01-00: 3-phase current input module with dedicated ground fault CT input channel
• MPU-CIM-02-00: 3-phase current input with residual ground fault calculation, no external GF CT required
• MPU-CIM-00-01: Standard current input module with RTD input expansion port enabled

Analog Input Modules (AIM)

• MPU-AIM-00-00: 6-channel RTD input module, PT100/PT1000 compatible, Celsius/Fahrenheit selectable
• MPU-AIM-01-00: 10-channel RTD input module for high-density thermal monitoring applications
• MPU-AIM-02-00: 4–20 mA analog input module, 4 channels, process variable monitoring

Digital Input/Output Modules (DIM / DOM)

• MPU-DIM-00-00: 8-channel 24 VDC digital input module, optically isolated, status monitoring
• MPU-DIM-01-00: 16-channel digital input module, 120 VAC compatible, extended voltage range
• MPU-DOM-00-00: 6-channel relay output module, Form C contacts, 5A @ 250 VAC rated
• MPU-DOM-01-00: 4-channel high-current relay output module, 10A @ 250 VAC, trip-duty rated

CPU / Base Modules

• MPU-32: Base CPU module, RS-485 Modbus RTU, 512-event log, standalone operation
• MPU-32E: Enhanced CPU module, dual RS-485, 1024-event log, harmonic analysis to 31st
• MPU-32E-ETH: CPU module with dual-port EtherNet/IP and Modbus TCP, SNTP time sync

Communications Adapter Modules

• MPU-CAM-00-00: DeviceNet communications adapter, Group 2 slave, 500 kbps max
• MPU-CAM-01-00: PROFIBUS DP adapter module, 12 Mbps, GSD file provided
• MPU-CAM-02-00: EtherNet/IP + Modbus TCP dual-protocol adapter, 100 Mbps

Power Supply Modules

• MPU-PSM-00-00: 24 VDC auxiliary power supply module, 20W output, DIN rail mount
• MPU-PSM-01-00: 120/240 VAC universal input power supply module, 30W, wide-range input

Sourcing Hard-to-Find & Obsolete MPU Series Parts

The MPU-32 base platform and first-generation CIM/AIM modules have reached end-of-active-production status. Littelfuse no longer manufactures replacement units for the MPU-32 (non-E) CPU module or the MPU-CAM-00-00 DeviceNet adapter. Plants operating these units face a sourcing gap that standard distribution channels cannot fill.

Quality Control for the MPU Series Range

MPU Series modules use a proprietary backplane bus operating at 5 VDC logic levels with differential signal pairs for inter-module communication. Standard bench testing with generic relay test sets is insufficient to validate backplane integrity. DriveKNMS applies the following test protocol to all MPU modules:

• Backplane bus continuity and impedance verification using MPU-compatible chassis fixture
• CT input accuracy test: inject calibrated 1A and 5A secondary signals, verify metering accuracy within ±0.5% of rated
• RTD channel verification: apply decade resistance box at PT100 reference values (0°C = 100Ω, 100°C = 138.5Ω), confirm displayed temperature within ±1°C
• Digital I/O functional test: cycle all input channels with 24 VDC test signal, verify output relay actuation and contact resistance <100 mΩ
• Communications loopback test: Modbus RTU register read/write verification across all defined function codes
• Firmware version identification and documentation prior to shipment